Tat is a regulatory protein of human immunodeficiency virus type 1 (HIV-1) produced very early after infection and essential for virus gene expression, replication and infectivity (Arya 1985; Fisher 1986; Chang 1995). During acute infection of T cells by HIV, Tat is also released in the extracellular milieu and taken-up by neighbour cells (Frankel 1988; Ensoli 1990; Ensoli 1993; Chang 1997) where, according to the concentration, can increase virus infectivity. Specifically, upon uptake Tat can enhance, in infected cells, virus gene expression and replication (Frankel 1988; Ensoli 1993; Chang 1997), and, in uninfected cells, the expression of the β-chemokines receptors CCR5 and CXCR4 favouring transmission of both macrophage and T lymphocyte-tropic HIV-1 strains (Huang 1998; Secchiero 1999). Extracellular HIV-1 Tat protein is also responsible for the increased frequency and aggressiveness of Kaposi's sarcoma (KS) a vascular tumor particularly frequent in HIV-infected individuals (Friedman-Kien 1981; Safai 1985). In particular, previous work from our and other groups indicated that Tat cooperates with angiogenic and inflammatory cytokines that are highly expressed in KS patients (Samaniego 1998; Ensoli 1994) in inducing new blood vessels formation (angiogenesis) and the growth and locomotion of spindle shaped cells of endothelial cell origin (KS cells) and of activated endothelial cells (Barillari 1992; Albini 1995; Ensoli 1994). Moreover, the sequence comprised between residues 21 and 40 (core domain) in the HIV-1 BH-10 Tat protein has been shown to act as a transactivator, to induce HIV replication and to trigger angiogenesis (International Patent number WO 00/78969 A1). In particular, our data have shown that biologically active Tat binds through its RGD region the integrin receptors α5β1 and αvβ3 and that this interaction mediates the adhesion, growth and locomotion induced by Tat on KS cells and endothelial cells activated by inflammatory cytokines (Barillari 1993; Barillari 1999a and 1999b). In addition, Tat acts also as a chemotactic factor for these cell types as well as for monocytes and dendritic cells (DC) (Albini 1995; Benelli 1998; Lafrenie 1996; Mitola 1997). Finally, our data demonstrated that KS and HUVE cell migration and invasion are toward the Tat protein is mediated by the binding of the Tat RGD region to the α5β1 and αvβ3 integrins (Barillari, 1999b). Consistent with these findings, the immune response to Tat has been shown to play a key role in controlling the progression of AIDS and AIDS-associated diseases. In fact, a Tat-specific immune response is present in HIV-1 infected subjects and simian immunodeficiency virus (SIV)-infected monkeys, and correlates inversely with progression to the symptomatic stage of the infection (Reiss 1990; Venet 1992; Rodman 1993; Froebel 1994; Re 1995; Van Baalen 1997; Zagury 1998; Addo 2001). Moreover, vaccination with biologically active Tat protein or tat DNA induces protection against SHIV89.6P virus replication and disease onset which correlates with the presence of Th-1 responses including specific cytotoxic T lymphocytes (CTLs) (Cafaro 1999; Cafaro 2000; Cafaro 2001, and PCT WO99/27958). The same protection data have been more recently observed with a tat-rev vaccine delivered with viral vectors in macaques (Osterhaus 2001). In contrast, a limited containment of the infection has been observed in monkeys vaccinated with inactivated Tat or Tat peptides, in which antibodies and T helper specific responses but no CTLs nor Th-1 responses had been induced (Goldstein 2000; Pauza 2000). Again, the repeated intradermal (i.d.) inoculation of monkeys with native and active Tat protein alone (in the absence of any adjuvant) at low doses (5-6 μg) selectively induced a Th-1 response and specific CTLs in the absence of any significant antibody production (Cafaro 1999 and PCT WO99/27958). These immunological results were recently confirmed in a new vaccination protocol in which native Tat alone was repeatedly inoculated i.d. in 4 monkeys (unpublished data), and are comparable to those induced by i.m. vaccination with tat DNA in a published (Cafaro 2001 and PCT WO99/27958) and in an ongoing study. Similarly, recent work performed in SIV-infected macaques indicate that anti-Tat CTLs are key to control early virus replication after primary infection and exert a selective immune pressure on the virus leading to the appearance of slowly replicating, less pathogenic escape mutants (Allen 2000). Finally, Tat is presented with major histocompatibility complex (MHC) class I antigen (Moy 1996; Kim 1997), hence inducing anti-Tat CTL (Cafaro 1999). Micromolar concentrations of recombinant Tat protein (often of unknown biological activity) or peptides encompassing the basic region of Tat have been shown to enter many different cell types (Frankel 1988; Mann 1991; Ensoli 1993; Chang 1997; Fawell 1994; Moy 1996; Kim 1997). The highly basic charge of Tat residues 48-57, in fact, enables the protein to bind to heparan sulphate proteoglycans (HSPG) that are present on the membrane of all cell types (Chang 1997; Rusnati 1998). After release from acutely infected cells, a fraction of extracellular Tat binds, through its basic residues, to the HSPG (Chang 1997). This protects extracellular Tat from proteolytic degradation, as previously found for several growth factors (reviewed in Raines and Ross, 1992). Upon the binding of its basic region to cell surface HSPG, Tat is internalised through a receptor-independent pathway (Frankel 1988; Rusnati 1998; Tyagi 2001). In fact, Tat residues 49-57 (in the BH-10 Tat sequence) have been indicated to be able to translocate an OVA peptide into the cytosol of DC and to sensitize CD8+ T cells to this peptide (Kim, 1997). Furthermore, the 47-57 Tat sequence (from the BH-10 variant), fused with several effector proteins, has been suggested to be able to deliver them to cells (International patent number WO 01/19393 A1). However, this internalization mechanism requires high (micromolar) concentrations of Tat, occurs with any cell type and it is not sequence-specific. In fact, it has been shown that mutations of this region, which do not change its basic charge, do not affect the properties of the Tat basic region (Barillari 1999b). Similarly, the substitution of the Tat basic region with that of HIV rev or other genes does not change Tat properties. In this regard, the basic region of Tat has been shown to be very similar to the arginin-rich region carried by the members of the small family of proteins known as penetratins, that are all capable of entering many cell types (Derossi 1998). In fact, arginin homopolymers have been shown to enter cells even more efficiently than Tat basic region (Derossi 1998).
The property of the Tat basic region of being internalized by cells has been exploited to deliver foreign proteins to a variety of cell types (Fawel 1994; Wender 2000; and WO 01/19393). To this purpose, foreign proteins have been conjugated or fused to the Tat basic region which has been used as a carrier for the protein to be transduced (Fawel 1994; Wender 2000; and WO 01/19393). However, the inventor believes that due to the ubiquitous expression of HSPG, Tat basic region cannot be used for selective targeting, delivery and/or uptake of Tat by specific primary cell types, including antigen presenting cells (APC).
APC initiate and drive the type of immune response upon encountering foreign molecules (Bancherau 1998; Bell 1999). Typical APC include monocyte-derived DC (MDDC), T cell blasts (TCB), B-lymphoblastoid cell lines (BLCL) and monocytes-macrophages (Bancherau 1998; Bell 1999). In addition, when activated by inflammatory cytokines also endothelial cells acquire APC functions (Pober 1988). Among these inflammatory cytokines, interleukin (IL)-1, tumor necrosis factor (TNF) and interferon (IFN)γ are key for endothelial cell activation (Pober 1988). Exposure to these cytokines increases in endothelial cells the expression of α5β1 and αvβ3, that are among the several cell surface receptors binding Tat (Barillari 1993, Fiorelli 1999; Benelli 1998; Kolson 1993; Sabatier 1991; Vogel 1993; Boykins 1999; Ganju 1998; Milani 1996; Mitola 1997 and 2000; Weeks 1993; Albini 1996 and 1998; Chang 1997; Lafrenie 1996; Morini 2000; Rusnati 1998). Among all these APC, DC are the most efficient APC and are key to the induction of immune responses against infections and tumors (Banchereau 1998; Bell 1999). Their function is associated with a high expression of MHC and costimulatory molecules (CD40, CD80, CD86) and with the production of cytokines known to activate T lymphocytes, and β-chemokines. Upon encountering the antigens, DC undergo a maturation process characterized by an increase of costimulatory molecules expression and by a reduction of their phagocytic and pinocytic capability (Banchereau 1998; Bell 1999). Further, due to the upregulation of the homing receptor CCR7 and to the downregulation of CCR5, mature DC migrate to lymph nodes where they present antigens to T lymphocytes (Banchereau 1998; Bell 1999).
Prior art indicates that the addition of Tat protein to DC blocks in these cells the extracellular calcium influx, the production of interleukin-12, and the uptake of apoptotic bodies (Zocchi 1997; Rubartelli 1997). As a result, it is predicted that profound impairment of important DC functions including antigen uptake, processing and presentation and induction of Th-1 responses should occur. Further, impairment of phagolysosomal fusion has been reported in peripheral blood monocytes upon exposure to Tat, suggesting impairment in this cell type of both microbicidal and antigen processing (and presentation) functions (Pittis 1996). Moreover, Tat has been reported to induce both monocytes/macrophages and lymphocytes to secrete IL-10 (Masood 1994; Badou 2000), while inhibiting IL-12 production in monocytes (Ito 1998). Finally, exposure of APC to Tat has been reported to impair their capability to organize cell clusters and to properly activate T cells (Mei 1997). Moreover, prior art indicates that Tat profoundly impairs also T cell functions including suppression of responses to mitogens anti-CD3 or specific antigens (Viscidi 1989; Benjouad 1993; Subramanyam 1993; Chirmule 1995; Wrenger 1996; Wrenger 1997; Zagury 1998), T cell hyperactivation (Ott 1997; Li 1997), and T cell apoptosis (Westendorp 1995; Li 1995; McCloskey 1997). Further, inoculation of biologically active Tat has been reported to be immunosuppressive in vivo (Cohen 1999). Part of the effects of Tat on the immune system have been related to upregulation by Tat of the chemokines receptors CCR5 and CXCR4 (Huang 1998; Secchiero 1999), or the direct interaction of Tat with the chemokine receptors CCR2 and CCR3 (Albini 1998a) or with other receptors including CD26 (Gutheil 1994), Flt-1 (Mitola 1997), KDR (Albini 1996; Morini 2000), that are expressed by immune cells, as well as by endothelial cells. Therefore, according to this previous art Tat is expected to drive a Th-2 type of immune response and/or to interfere with or abolish proper APC function and T cell activation.
By contrast, our novel and unexpected finding, supported by experimental evidence exhibited in this patent application, indicate that: (i) APC are specifically targeted by Tat that selectively recognises and enters these cells at pico-nanomolar concentrations, but that this requires the interaction of native, substantially monomeric, biologically active Tat with α5β1, αvβ3 integrins, through the Tat RGD sequence; (ii) and that native, substantially monomeric, biologically active Tat activates, rather than inhibiting, APC function and induces, rather than suppressing, Th-1 type immune responses against itself and, most notably, other antigens. Specifically, our data show that Tat acts not only as an antigen but also as an adjuvant with potent immunomodulatory properties. These properties of Tat, namely of being selectively internalised as biologically active protein by APCs at picomolar-nanomolar concentrations and to act as an adjuvant, are strictly related each other. In particular, we have found, that Tat RGD sequence is key for the internalisation of active Tat by these cells through the α5β1 and αvβ3 integrin receptors. In fact, antibodies or competitor ligands blocking these integrins completely abolish or greatly reduce the uptake of picomolar-nanomolar concentrations of Tat, respectively. This uptake is very rapid, is dose-, cell maturation/differentiation- and time-dependent. Even more unexpectedly, we did not obtain similar results with other APC including monocytes, T cell blasts, or B cell blasts or non-activated endothelial cells. Therefore, these findings are completely novel since prior art indicates that Tat is taken up only at much higher concentrations (micromolar range), through its basic region, by a non-receptor-mediated pathway (Frankel 1988; Mann 1991; Rusnati 1998; Tyagi 2001). This internalization pathway occurs with any cell type, and it is not maturation/differentiation-dependent.
Further, we have found that Tat in its native, substantially monomeric, and biologically active form is absolutely required to observe all the above novel effects which do not occur when Tat is oxidized and inactivated. In fact, Tat has 7 cysteines and it is extremely sensitive to oxidation which, when occurring, causes the loss of native protein conformation and consequent loss of biological activity (Frankel 1989). Therefore, Tat is likely to lose its native conformation and activity when purified with procedures that are not specifically designed at maintaining this protein in its native form. Although established concepts in the field claim that biologically active Tat is toxic (Gallo 1999; Sabatier 1991; Kolson 1993; Westendrop 1995; Purvis 1995), by contrast, the highly purified, biologically active preparations of recombinant Tat utilized by the inventor has no cytotoxic nor pro-apoptotic effects on endothelial cells, DC, macrophages, other cell type tested, nor in vivo in mice or monkeys (Ensoli 1994; Barillari 1999a; Zauli 1993, 1995a and 1995b; Cafaro 1999, 2000 and 2001).
Thus, the inventor believes that full-length, wild type, native, substantially monomeric, and biologically active Tat from any HIV variant or its fragments or derivates containing the RGD region can be used as a highly efficient system for the selective targeting and delivery of molecules to specific cell types expressing the integrins recognized by the Tat RGD region (Barillari 1993, 1999a and 199b; Ensoli 1994). Given the very large amount and ubiquitous distribution of DC, macrophages and endothelial cells in the human body, the inventor believes that the capability of biologically active Tat or its fragments or derivatives containing the RGD sequence of targeting these APC and of driving Th-1 type cellular responses will offer a unique opportunity to, 1) to deliver cargo molecules to these cell types which represent a specific target for Tat and are recruited and activated in infections, pathologic angiogenesis, inflammatory diseases and tumors in the delivery system embodiment of the present invention; 2) induce a potent immune response against not only Tat but also against other antigens delivered by or with Tat, in the vaccine-adjuvant and immunomodulatory embodiment of the present invention. This belief is strongly supported by the successful previous work of the inventor with biologically active Tat as a vaccine to control HIV replication and to block disease onset (Cafaro 1999; Cafaro 2000; Cafaro 2001, and PCT WO99/27958) as opposed to inactivated Tat protein (Goldstein. 2000; Pauza 2000).
The present patent application is substantially different and innovative as compared to our previous patent application WO 99/27958 in many aspects. In fact, the above mentioned application claimed biologically active Tat or Tat encoding DNA to be effective as a vaccine against HIV/AIDS. At the time when said patent application was filed it was not known to us that low (picomolar-nanomolar) amounts of biologically active Tat, or its fragments or derivatives containing the RGD region, (i) specifically target APC and thus we could have not claimed its use as a carrier to selectively deliver cargo molecules to them; (ii) cause EC and DC cell maturation and activation and induce Th-1 type immune responses against different antigens, and thus we could have not claimed its use as a adjuvant and immunomodulator.
Thus, in this invention, biologically active Tat is proposed, in the first embodiment, as a delivery system to deliver to APC (i) different antigens or combinations of antigens for vaccination against different infectious diseases (not only HIV/AIDS) and tumors, or for multivalent vaccination against one or more infectious diseases, and (ii) therapeutic molecules for the treatment of infectious, inflammatory and angiogenic diseases and tumor growth and metastasis; and in the second embodiment, biologically active Tat is proposed as an adjuvant to drive T-cell mediated immune responses against different antigens, and in particular to enhance the immunogenicity of poorly immunogenic antigens, such as those expressed by certain intracellular pathogens as well as tumor cells, by combining or fusing them with biologically active Tat or its fragments or derivatives containing the RGD region.
In summary, the most important innovative aspect which makes the difference with the prior art is that here native, substantially monomeric, and biologically active Tat is claimed as a molecule which exerts different functions, i.e. it is a carrier to selectively deliver antigens to APCs or active compounds to specific tissues, and an adjuvant stimulating immune responses to other antigens. This unexpected properties make native, substantially monomeric, and biologically active Tat suitable for different applications in different infectious diseases (not only AIDS), inflammatory and angiogenic diseases and tumors.
Thus, the inventor believes that native, substantially monomeric, and biologically active Tat, fragments or derivatives thereof, containing the RGD sequence, acts with at least one of the following actions: as delivery system to specific APC or as an adjuvant, and claims that it can be exploited for preventive and therapeutic vaccination and/or drug delivery for the prevention and treatment of HIV/AIDS, other infectious, inflammatory, and angiogenic diseases.